Safety-control switch



Aug. 12, 1930. F. F. BAHNSON SAFETY CONTROL SWITCH Filed Dec. 17 1926jnmnto c Grammy.

Patented Aug. 12, 1930 PATENT OFFICE FREDERIC F. BAHNSON,

BAHNSON COMPANY, OF WINSTONSALEM, NORTH NORTH CAROLINA OF WINSTON-SALEM,NORTH CAROLINA, ASSIGNOI\T0 THE CAROLINA, A CORPORATION OFSAFETY-CONTROL SWITCH Application filed December 17, 1926. Serial No.155,517.

This invention relates toelectrieal control switches and moreparticularly to that class of switches which is operated by hygroscopicelements thermostats or the like. and which are used to operate controlsfor temperature,

humidity etc.

An object of this invention is to provide a switch in which thefrictional resistance op posing the, operation of the switch is reduced1 to a minimum.

Another object is to provide a safety switch wherein the expansion andcontraction of'the actuating element cannot injure the switch or alterthe adjustment thereof, even when such expansion and contraction go farbeyond that normally occurring in such elements.

A further object is.to provide a switch with simple and accurateadjustments for the con- 29 tacts thereof. a

A further object is to provide a switch for operation by a hygroscopicelement or the like wherein an adjustable mounting for the hygroscopicelementis provided on the switch casing.

These and other objects will be apparent from the following descriptiontaken in connection with the accompanying drawing wherein i F i g. 1 isa section of the complete switch.

Fig. 2 is a section of line 2-2 thereof. Fig. 3 is a partial section ofa modification. Fig. 4 is a section on line 4-4 thereof. Referring tothe drawings, numeral 1 indicates a base for the switch mounting,preferably of metal, having an upper enlarged face plate 2. Upon theface plate 2 are bolted two insulating plates 3 and 'l by bolts 5. i

plunger (5 extends through alined openings in.

the base 1 and plates 3. l, the opening in base 1 being of such diameterthat the base 1 serves as a guide for plunger 6. and the opening in theplate 3 being (Ollllltl'llOlttl from its upper surface.

Seated in the opening in plate. 3 is an internally threaded ring 7.which is electrically connected to a binding post: 8. '.lhreaded intothe ring 7 is a disk contact 9. which is also perforated to allowplunger 6 to pass freely thercthrough. A movable contact disk 11 iscarried by a shoulder 10 on the plunger and is normally contained withinthe opening in plate 1. A coil spring 12 surrounds the plunger 6 and itslower end rests upon disk 11, the upper end of the spring being fixed inan insulating cover 13 carried from base 1 by bolts l i. A terminal 15on cover 13 is electrically connected to the spring 12, and through thespring with the movable contact disk 11.

It is here noted that contact disk 11 fits loosely on the plunger 6, sothat it may have a slight rocking motion thereon to adjust itself to thestationary contact 9. Contact disk 11 has been shown as metallic but itwill be clear that this member could be of insulating material withsuitable contacts thereon.

Resting upon the upper face of insulating plate 4 is an annular member16 having a threaded passage tlierethrough which overlies thecounterbored end of the axial passage in which plunger (3 moves. Acontact disk 16 is screw threaded into the outer ring 16 and may bevertically adjusted therein. The annulus 16 is of conducting materialand has a shoulder upon which is seated a coil spring 17, enclosing coilspring 12, but spaced :1 material distance therefrom. This spring 17holds annulus 1G yieldingly against plate 4 and presses at its other endagainst the cover 13, being connected to binding post 18 thereon.

Enclosing the springs 12 and 17 and C()l1- tact 16 is a cylindricalinsulating casing 19 clamped between plate 4 and cover 13. i

Secured to the lower side of the base 1 are two guideways 20 forslidably receiving the hydroscopic element or the like. in this caseshown an expansible wooden block 21.

Sliding plates 22. 23.. of metal or other hard material, are provided atthe upper and lower ends respeclivclv of th" lrvgriismipicele- [pent 21to prevent damage to the element by the plungeutl, and an adjustingscrew 21 which is mounted in the base of: the guideway.

lt is believed that the operation of the device as thus described willbe readily I1ndcrstood. Upon expansion ot the member ll the plunger 6rises. carrying contact disk contact between 11 and 16'.

11 with it. thereby breaking the normal contact between 11 and 9, andupon a continued predetermined rise of the plunger, making Since bothcontacts 9 and 16 are adjustable in the line of movement of contact disk11, it is apparent that various ranges of movement of the operatinghygroscopic element or the like may occur before the circuits are madeor broken. If the element continues to rise after contact disk 11engages contact 16, no injury can result to the switch, as these twocontacts simply move upward, the spring 17 allowing a wide range ofmovement. Since the straight line motion of plunger 6 reduces thefriction to a minimum, the switch may be actuated by relatively smallforces.

Also, if the element contracts or descends after disk 11 again rests oncontact 9, no harm is done since the upper brass plate 24 merelyseparates from the plunger 6.

In the modification shown in Figs. 3 and 4, a bi-metallic element 25operates the switch. This element contacts with the lower end of plunger6 and is tightly clamped in an internally threaded carrier 26. Thiscarrier is adjustably supported in a slotted frame 27 by means of ascrew-threaded member 28 upon which the carrier 26 is threaded.

By turning the knurled head of screw 28, the carrier 26 is raised orlowered to adjust ele ment 25. The frame 27 is supported from the maincasing by a rigid arm 27.

It will be understood that the use of the terms vertical and horizontalthroughout the specification and claims are not to be construed aslimitations but are merely used for convenience of description. Thesafety control switch is equally capable of operation in other positionsthan that shown.

It is to be understood that the invention is not restricted to theembodiment herein shown and described, as the construction andarrangement of the *arious elements are subject to considerablemodification without departing from the spirit of my invention. F orexample, the upper and lower contact disks may be carried directly bythe plates 3 and at if the switch is to be used in control systems inwhich no adj ustment'of the switch is necessary. The initial adjustmentof such a switch will be determined by the relative thickness of themovable contact disk 11 and plate a. In control systems having a singlecircuit which is tov be opened or closed by the switch, either the upperor lower contact disk will be unnecessary.

These and other modifications in the various parts, their relativeshape, size and arrangement may be made without depart ing from thespirit of my invention as set forth in the following claims.

I claim 2- 1. An electric circuit maker and breaker for operation by ahygroscopic element or the like comprising a stationary base, a plungerpassing through a counter-bored passage in said base and adapted forreciprocating movement by the hygroscopic element, a contact diskcarried by said plunger, sa d disk being of such thickness that it maybe com pletely received by the counter-bored portion of said passage,and a contact carried by said base above said passage, for engagement bysaid contact disk upon upward movement of said plunger.

2. The structure as in claim 1 wherein the contact is yieldingly heldagainst said base by a spring.

The structure as in claim 1. wherein a spring yieldingly opposes theupward move ment of said plunger and disk.

4. The structure as in claim 1 whe ein the disk is yieldingly held inthe counter-bored portion of said passage by a. coil spring and thecontact is yielding-1y held against the face of said base by a secondcoil spring enclosing the first spring.

5. The structure as in claim 1 wherein a cover is rigidly connected tosaid base. a coil spring presses against said cover and is conne ted tothe said disk. a second coil spring encloses the first spring andpresses against said cover and said contact. and a jacket is arrangedbetween the base and cow er to enclose said springs.

6. The structure as in claim 1, wherein said contact comprises twoparts. the part engageable by said disk being vertically adjustable withrespect to the part which engages said base.

7. The structure as in claim 1, wherein a stationary contact is carriedby said base beneath said contact disk.

8. The structure as in claim 1 wherein a second contact is carried bysaid base beneath said disk, said second contact being verticallyadjustable on said base.

9. An electric switch adapted for operation by a hygroscopic element, orthe like, comprising a supporting base having a passage therethrough, aplunger carried by said base and guided for reciprocating movement bythe walls of said passage, a contact disk on said plunger, :1 contactresting on said base for engagement by said disk, aspring urging saidcontact toward said disk. and means on said base suppi'irting avhygroscopic element or the like for contacting engagement with saidplunger to more the sameto press said disk into engagement with saidcontact.

In testimony whereof I :rliix my signature.

FREDERIC F. BAHNSON.

